(c) as soon as practicable after installation of the same on the
 Aircraft but, in any event, no later than the earlier of (i)
 the next Major Check or Engine Shop Visit (as applicable) or
 (ii) the Final Expiry Date, Lessee or, where there is a
 permitted sublease in place, the sub-lessee thereunder,
 removes any such engine or part and replaces it with the
 Engine or Part replaced by it or by an engine or part, as the
 case may be, complying with Clause 8.13 above.

 8.17 POOLING OF ENGINES AND PARTS:

 Without prejudice to its rights pursuant to Clauses 8.14(d) and
 8.15(c), Lessee shall not without the prior written consent of
 Lessor, which consent shall not be unreasonably withheld or delayed,
 permit or enter into any agreement or arrangement for the pooling or
 interchange of any Engine or Part with any other Person.

 8.18 EQUIPMENT CHANGES:

 (a) Lessee shall not make any modification or addition to the
 Aircraft (each an "Equipment Change"), except for an Equipment
 Change which:

 (i) is completed in connection with the post-Delivery
 installation of the In-flight
 Entertainment/Communications System (IFE) or the
 Winglets; or

 (ii) is expressly permitted by this Agreement; or

 (iii) does not diminish the value, utility, condition, or
 airworthiness of the Aircraft and either (aa)
 constitutes a modification to the class configuration or
 passenger seating in the cabin, or (bb) has a cost of
 less than US$250,000, or (cc) has the prior written
 approval of Lessor which approval shall not be
 unreasonably withheld or delayed; or